Leafy sea dragon

The leafy sea dragon or Glauerts Seadragon,[1]Phycodurus eques, is a marine fish in the family Syngnathidae, which also includes the seahorses. It is the only member of the genus Phycodurus. It is found along the southern and western coasts of Australia. The name is derived from the appearance, with long leaf-like protrusions coming from all over the body. These protrusions are not used for propulsion; they serve only as camouflage. The leafy sea dragon propels itself by means of a pectoral fin on the ridge of its neck and a dorsal fin on its back closer to the tail end. These small fins are almost completely transparent and difficult to see as they undulate minutely to move the creature sedately through the water, completing the illusion of floating seaweed.

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Description

Much like the seahorse, the leafy sea dragon's name is derived from its resemblance to another creature (in this case, the mythical dragon). While not large, they are slightly larger than most sea horses, growing to about 20–24 cm (8–10 in). They feed on plankton and small crustaceans.

The lobes of skin that grow on the leafy sea dragon provide camouflage, giving it the appearance of seaweed. It is able to maintain the illusion when swimming, appearing to move through the water like a piece of floating seaweed. It can also change colour to blend in, but this ability depends on the sea dragon's diet, age, location, and stress level.

The creature has a long, pipe-like snout that it uses to feed. It primarily eats crustaceans including plankton and mysids, but its diet also includes shrimp and small fish. It catches prey with the aid of its camouflage. Leafy sea dragons oddly enough do not have teeth, which is rare amongst animals that eat small fish and shrimp.

The leafy sea dragon is related to the pipefish and belongs to the family Syngnathidae, along with the seahorse. It differs from the seahorse in appearance, form of locomotion, and its inability to coil or grasp things with its tail. A related species is the weedy sea dragon, which is multi-coloured and grows weed-like fins but is smaller than the leafy sea dragon. In the November 2006 issue of National Geographic, marine biologist Greg Rouse was reported as investigating the DNA variation of the two sea dragon species across their ranges.

Reproduction

As with seahorses, the male leafy sea dragon cares for the eggs. The female produces up to 250 bright pink eggs, then deposits them on to the male's tail via a long tube. The eggs then attach themselves to a brood patch, which supplies them with oxygen. It takes a total of nine weeks for the eggs to begin to hatch, depending on water conditions. The eggs turn a ripe purple or orange over this period, after which the male pumps its tail until the infants emerge, a process which takes place over 24–48 hours. The male aids in the babies hatching by shaking his tail, and rubbing it against seaweed and rocks. Once born, the infant sea dragon is completely independent, eating small zooplankton until large enough to hunt mysids. Only about 5% of the eggs survive. Leafy sea dragons take about 28 months to reach sexual maturity.[3]

Movement

The leafy sea dragon uses the fins along the side of its head to allow it to steer and turn. However, its outer skin is fairly rigid, limiting mobility.

Individual leafy sea dragons have been observed remaining in one location for extended periods of time (up to 68 hours) but will sometimes move for lengthy periods. Tracking of one individual indicated it moved at up to 150 metres (490 feet) per hour.[4]

Threats

Leafy sea dragons are subject to many threats, both natural and man-made. They are caught by collectors, and used in alternative medicine. They are vulnerable when first born, and are slow swimmers, reducing their chance of escape from a predator. Seadragons are often washed ashore after storms, as unlike their relative the seahorse, seadragons cannot curl their tail and hold onto seagrass to stay safe.

They have become endangered through pollution and industrial runoff as well as collection by fascinated divers who are entranced by their unique appearance. In response to these dangers they have been officially protected by the Federal Government of Australia.

Habitat

The leafy sea dragon is found only in the waters of Australia from Kangaroo Island on the Southern shoreline to Jurien Bay[5] on the Western shoreline. It was once thought to be very limited in its range; however, further research has discovered that the sea dragon will actually travel several hundred metres from its habitat, returning to the same spot using a strong sense of direction. They are mostly found around clumps of sand in waters up to 50 metres (164 feet) deep, hiding among rocks and sea grass. They are commonly sighted by scuba divers near Adelaide.[6]

In captivity

Due to being protected by law, obtaining sea dragons is often an expensive and difficult process as they must be from captive bred stock, and exporters must prove their broodstock were caught before collecting restrictions went into effect, or that they had a license to collect dragons. To date, only the Tennessee Aquarium in Chattanooga, Tennessee has been able to breed the leafy sea dragon. It first succeeded in doing so in 2003. Sea dragons have a specific level of protection under federal fisheries legislation as well as in most Australian states where they occur.[7]

Sea dragons are difficult to maintain in aquaria. Success in keeping them has been largely confined to the public aquarium sector, due to funding and knowledge that would not be available to the average enthusiast.